The answer seems to be yes, but I will dig deeper. In theory because Firefox OS is just HTML5, you can use anything that would be HTML5 based. For example, Google AdSense should work, though you may need to put those in an IFrame and ask Google to enable a new window as a target.

On the other hand, anything that works with Construct 2 ads for, say, HTML5 platforms such as Chrome and Tizen should also work, maybe even Cocoon.js. I don't know what Construct 2 target platforms accept for ads.